- Understand the stresses experienced by emergency responders during fire suppression or other extended incidents.
- Describe the functions and operations of on-scene rehab.
- Understand the physiological response of the body to environmental stresses.
- Identify exertional heat illness and describe the treatments.
- Describe the available modalities for rehydration and core temperature cooling.
It's a hot, humid day in August when Engine 219-1 arrives first on the scene at a commercial structure fire. The crew advances a 2.5" hose into the warehouse to begin an interior attack. With the arrival of truck 219, a crew is sent to the roof to ventilate. When it's learned that the warehouse foreman can't be found, a second crew is sent into the structure to search for the missing man.
The victim is ultimately located, unconscious but alive, and is extricated from the building. He's placed in the only ambulance on scene and rushed to the hospital. After multiple entries and changes of SCBA cylinders, the crews bring the fire under control.
The incident commander orders the first-arriving crews to report for rehabilitation while the second alarm crews begin the overhaul.EMS has left the scene with the extricated patient, so the crews remove their turnout coats and begin to drink bottled water on their own.
One firefighter complains of being unusually tired. He looks pale and diaphoretic. When the crew picks up their gear to return to the scene, the firefighter loses consciousness and strikes his head on an SCBA cylinder when he falls to the ground. Other firefighters tend to the man while a second ambulance is called to the scene.
What do baking, athletics and firefighting all have in common? All of these professions have had members die of heat-related illness. Exertional heat illness can be a deadly process by itself, but when additional stress is placed on the cardiovascular system, it can increase a person's risk for myocardial infarction, stroke or sudden cardiac arrest. Although exertional heat illness can't be entirely eliminated from firefighting, it should never be fatal when proper medical supervision and appropriate rehabilitation services are available.
Firefighters suffer more than 80,000 injuries and nearly 100 line-of-duty deaths each year. Although the risk of morbidity and mortality rises dramatically when performing fire suppression at a non-residential structure, most firefighter injuries occur during fire suppression at single- and two-family homes. More than half of firefighter deaths are due to cardiovascular events, and nearly a quarter of the injuries are attributed to overexertion and strain.(1)
Fire suppression is a physiologically stressful activity requiring the firefighter to work at near-maximal heart rates for extended periods. The firefighter is exposed to a combination of heat from the fire and environment, and the metabolic heat generated from the heavy exertion. When combined with heavy thermal protective clothing, thermoregulation is impaired and core body temperature begins to rise.
The heat burden and loss of plasma volume from sweat forces the heart to work harder. This may cause heart rates to be persistently elevated, even after the firefighter leaves the scene and removes the protective clothing. For example, at one training fire, we measured a core body temperature of 103_ F (39.4_ C) in an asymptomatic instructor associated with a heart rate of 170 beats per minute.
Although first responder rehab will most often be implemented on the fireground, it should also be considered essential in other types of incidents. For example, hazardous materials technicians will often employ splash- and vapor-resistant personal protective equipment that impairs thermoregulation, resulting in rising core temperatures. An organized rehab sector may also be required at an extendedEMS incident if conditions require long periods of work outdoors without sufficient protection from the sun and weather.
The role of the rehab sector is to provide: 1) medical evaluation and treatment; 2) rehydration and nutrition; 3) protection from the elements; 4) supervised rest and recovery; and 5) firefighter accountability.(2)Although this article focuses on fireground rehab at hot weather incidents, it's important to remember rehab is required for every environmental condition.
Heat stress placed on responders is both intrinsic (metabolic heat produced by the individual) and extrinsic (heat from exposure to open flame or heated areas, and the environment). Under normal conditions, the body sheds additional heat byconduction, convection, evaporation, respiration and radiation. Of these, evaporation of sweat and convection to air or circulating water are most efficient.
Although constantly improving, the thermal protective clothing worn by firefighters impairs both evaporation and convection processes. Even if moving air were blown onto the firefighter, the thick layers of the garment hamper effective convection. Further, thick layers of turnout gear impede the evaporation of sweat, causing it to collect in the garment and gradually increase the weight of the gear during the incident. Impairing thermoregulation ultimately results in a rising core body temperature. Even if the heat stress doesn't progress to exertional heat illness, a firefighter usually suffers some consequence from the additional heat burden.
Environmental conditions can also magnify heat stress during an incident. Thermal burden is increased with rising temperature andrelative humidity. Warm air can hold more moisture than cold air, intensifying the problem during warm weather. As the relative humidity rises, evaporation is inhibited and causes sweat to accumulate on the skin surface once thermal protective garments have been removed. Air temperature and relative humidity together create the heat index, the temperature ˙experiencedÓ by the firefighter. In the desert, a temperature of 92_ F with a relative humidity of 10% feels like 87_. The same 92_ F day during aPittsburgh summer with 70% relative humidity feels like 155_ and can rapidly lead to exertional heat illness.
When considering the heat index, any temperature over 90_ F should be treated as dangerous in terms of personnel working in thermal protective clothing. Under these conditions, it's imperative that an effective rehab section be established at every major incident fire so crews can be regularly assessed for heat stress and receive appropriate preventative treatment.
Cardiovascular Stress Ï Blood
Heat stress also affects blood clotting and clot resolution.(3) With heat stress comes co-activation of coagulation (which makes blood thicker) andfibrinolysis (which makes blood thinner). As the body temperature returns to normal, fibrinolysis down-regulates to its normal level while coagulation remains activated for a period of time. This results in the blood being ˙thickerÓ than normal under heat-stressed conditions.
Combined with an increased endogenous epinephrine surge and the cardiovascular stress from the strenuous work associated with fire suppression, the addition of ˙activatedÓ coagulation to these traditional cardiac stressors can accelerate the progression to myocardial infarction, resulting in a crippling heart attack or sudden death.
Cardiovascular Stress Ï Sweat
Although evaporation is impaired when a firefighter is wearing turnout gear, sweat is still produced when warm blood moves from the body core and travels to the skin surface. Production of sweat removes water from the plasma, thus reducing the effective blood volume.
The resultinghypohydration reduces the stroke volume of every cardiac contraction. To maintain the cardiac output, the heart must beat faster to ensure sufficient blood is delivered to working muscles and vital organs.
Additional hypohydration will result in a loss of cardiac output if the rising heart rate and falling stroke volume can't maintain the body's need. When combined with the additional heat load, this combination of stressors make the heart endure near-maximal heart rates for extended time intervals.
Cardiovascular Stress -- & Tears (Smoke Exposure)
Exposure to smoke and particulate matter created from combustion at a fire are known environmental hazards that can stress the cardiovascular system. Although firefighters routinely wear self-contained breathing apparatus (SCBA) during fire suppression, overhaul operations are often conducted without respiratory protection. The byproducts of combustion, a complicated mixture of chemicals, are suspended in the air during overhaul, posing a hazard to the firefighters inside the structure. Two common chemicals associated with significant risks are carbon monoxide (CO) and hydrogen cyanide.
CO is present in high concentrations during the overhaul phase of fire suppression.(4) When inhaled, it binds tightly to hemoglobin, formingcarboxyhemoglobin and impairs oxygen delivery. Some level of carboxyhemoglobin is expected simply from living in an urban environment or from smoking cigarettes. However, when the level in the blood rises due to significant or prolonged exposure, the resulting hypoxia may induce myocardial infarction.
Carbon monoxide is difficult to clinically identify in the prehospital setting. However, handheld devices (CO-oximeters and breath analyzers) capable of measuring CO bound to hemoglobin are now available and being deployed to monitor firefighters during rehabilitation.
Hydrogen cyanide is formed from the incomplete combustion of many common materials, including paper, cotton, silk and plastic. Hydrogen cyanide binds to proteins in the cell mitochondria and disrupts the use of oxygen.
It's likely that hydrogen cyanide poisoning has always been a problem on the fireground but has only recently been recognized. In March 2006, a series of routine structure fires inProvidence,R.I., sent 28 firefighters to the hospital with headaches, dizziness and incoherence. Eight were found to have elevated levels of cyanide in their blood. A new cyanide antidote kit has been approved by the FDA (Hydroxocobalamin, Cyanokit from Dey, L.P., Merck KGaA ofDarmstadt,Germany) and should be available to hospitals that treat firefighters exposed to smoke.
It's important to remember that standard pulse oximeters cannot identify carboxyhemoglobin nor can they account for hydrogen cyanide in the cells. For patients poisoned with either of these gases, the SO will likely appear normal, even though the patient is displaying signs and symptoms of hypoxia.
Finally, the particulates found in fire smoke have both acute and chronic cardiovascular effects. Short-term exposure can trigger myocardial infarction, especially among those with pre-existing heart disease.(5) Long-term exposure may speed or change the process of atherosclerosis, creating a medical condition that increases the risk of myocardial infarction and stroke.(6,7)
The NFPA 1584: Recommended Practice on Rehabilitation for Members Operating at Incident Scene Operations and Training Exercises(2003) is a consensus document outlining recommendations for incident rehabilitation. This document will be beneficial to any organization developing rehab procedures but can be customized to meet the capabilities and needs of your organization and the environment (hot/cold) in which you customarily operate. We maintained the spirit ofNFPA 1584 in this article, but we've supplemented that guideline with recommendations from the sports medicine and exercise physiology literature.
Rehab operations can be divided into two phases: immediate and formal. Many fire departments operate on the ˙two-cylinder rule,Ó in which two full SCBA cylinders can be consumed during fireground operations before the firefighter must enter the rehab sector. When following this rule, the firefighter is expected to perform immediate rehab during the first-cylinder change.
Immediate rehab is also called ˙self-rehab.Ó For self-rehab, firefighters consume liquids while changing their SCBA cylinder. This allows for initial rehydration before re-entering the incident. For self-rehab to be effective, the fluids must be readily available to all fire companies. One method to ensure firefighters have the opportunity to perform self-rehab is to place bottles of water or sports drink with spare SCBA cylinders. This guarantees they're at hand when the firefighter returns to the apparatus for the second cylinder.
For short-duration incidents, self-rehab may be all that's required. However, for incidents extending beyond the second SCBA cylinder, a formal rehab sector must be established. It's the incident commander's (or safety officer's) responsibility to ensure crews are rotated through the rehab sector.
There are many possible solutions for incident rehab. We've attempted to answer the most common questions withgood, better andbest strategies.
Where do I set up a rehab sector?
Good: At a minimum, the rehab area must provide shelter from the sun and heat or the cold depending on the time of year. Be sure to keep the sector away from running vehicles to prevent exposure to CO and diesel exhaust, and if possible, place the rehab sector out of sight of the incident. A rehab area can be created using a tent and folding chairs, allowing a firefighter to remove turnout gear and be seated. Add fans on hot days and portable heaters on cold days. If using gas-fired torpedo heaters, be sure to monitor the sector with a four-gas meter to avoid CO exposure.
In the case of a high-rise fire, the optimal place for rehab may be a few floors from the fire floor, a safe distance from fire suppression but close enough to allow reasonable access to the incident.
Better: The easiest way to provide shelter is to use a vehicle equipped with heat and air conditioning. Many fire departments are now ordering apparatus with air-conditioned closed cabs. Some of these vehicles are sufficiently large enough to allow for four to six individuals to enter the vehicle to escape the environment.
A large ambulance can also be used for rehab. However, don't commit an ambulance that's tasked with transporting patients. It'll be difficult to evict four or five firefighters from the back of the rig if a medical emergency occurs. In cities with an established transit system, emergency agencies can often request a bus to be available on scene for rehab.
Best: The optimal rehab sector is established by a specialty vehicle designed for this task. A large ambulance or small bus can be fitted with rehab equipment and dispatched as needed. For departments with smaller run volumes, it may be possible to share this resource across multiple agencies. A designated rehab vehicle has the advantage of placing medical and rehab equipment in the same vehicle. Placing tents on the vehicle allows for rapid expansion of the rehab sector during larger incidents or on days with mild weather.
How should I monitor personnel in the rehab sector?
Good: At a minimum, all personnel in the rehab sector should be logged in (and out) and have vital signs monitored every ten minutes. Repeated vital signs demonstrate trends toward improvement or deterioration once the individual is cooled and rehydrated.
Initially, all personnel who have been involved with strenuous activity, fire suppression or suppression support in a warm or hot environment will likely be tachycardic and have rapid respirations, due to the combined effects of exertion and mild hyperthermia.
Breathing and heart rates that remain elevated after providing fluids and cooling signal a worsening condition, and should be evaluated by a physician. Additionally, abnormal blood pressures should have the cause identified and treated; however, a normal blood pressure doesn't rule out cardiovascular strain.
Better: Baseline vital signs have been recorded for all emergency personnel and made available to rehab staff both during rest and after a fixed period of aerobic exercise (e.g., standardized one-mile run/walk). This data should be kept with rehab supplies or vehicles, and updated annually. Knowing the individual's vital signs after exercise without the addition of heat stress allows the rehab officer to make rational decisions about returning a firefighter to the incident.
In addition to monitoring vital signs, assessing the responder's temperature adds to the clinical picture when assessing them in the rehab sector. There are many types of thermometers available. True core temperature is different than most commonly measured temperatures (i.e., oral, tympanic, etc). Although most high-quality thermometers read accurately on normothermic people at ˙room temperature,Ó device limitations are revealed when monitoring hyperthermic individuals who are performing physical exertion in adverse environments.
Oral and tympanic thermometers are most common. Tympanic thermometers are very sensitive to position in the aural canal. If the tip of the thermometer is not facing the middle ear, falsely low readings will be obtained. Oral thermometers are reliable in the lingual pocket but will read falsely low if used after fluids have been consumed or if the person is breathing rapidly. One study compared oral thermometers with tympanic in firefighters after exiting a training fire and found the readings poorly correlated.(9)
Temporal thermometers have become more popular in health-care settings. These thermometers move across the skin of the forehead and behind the ear to measure the blood temperature in the temporal artery. However, although these devices appear accurate in pediatric patients, studies have found they're not as reliable in adults. Finally, adhesive thermometers placed on the forehead have been shown to be accurate in exercising athletes. However, these items may not work correctly during cool weather conditions. Regardless of the thermometer you choose, it should be used only to augment the clinical picture.
Best: The ultimate adjunct to a rehab protocol is measuring body weight. Normal body weight in a standard work uniform should be obtained monthly and entered into a rehab database, so emergency personnel can be weighed in the rehab sector wearing a work uniform to estimate how much fluid has been lost through sweating. Remember to correct for sweat soaked into the uniform. In our system, we estimate sweat-soaked clothing at 0.5 kg. If a firefighter is standing on the scale in sweat-soaked clothing and the scale displays a normal weight, we assume they've lost 0.5 kg of fluid and rehydrate them accordingly. This technique requires the purchase of accurate, reliable scales and continuous monitoring of normal body weight.
How do I rehydrate in the rehab sector?
Good: The traditional fluid used for rehydration, bottled water, is cheap and easy to store for extended periods. For every kilogram of fluid lost, a kilogram must be replaced. That means the typical weight loss of one kilogram experienced by a working firefighter will require 34 oz. of water to ensure full rehydration. Many individuals may not voluntarily consume this quantity, so intake should be encouraged and documented for each individual on the rehab sector log.
Caffeinated beverages are perhaps the most misunderstood fluid in the context of rehydration and performance. Caffeine stimulates the sympathetic nervous system and is generally considered in sport to be anergogenic aid that improves continuous exercise time to exhaustion.
It's widely believed that caffeine exerts a diuretic effect that will impair performance in the heat. Contrary to popular belief, there's no evidence that caffeine consumption results in water-electrolyte imbalance or reduced exercise heat tolerance.(10) However, the stimulant effect will raise the heart rate, which isn't helpful in the context of fireground rehab. Therefore, we recommend avoiding caffeine in the rehab sector.
Better: Sport drinks are often ignored by the emergency service organizations due to a misconception of rehydration. It's a common belief that sport drinks cause gastric distress and lead to further dehydration by pulling water from the cells. On the contrary, a drink that includes glucose and sodium chloride should be considered for prolonged incidents or if there's inadequate access to meals or during the initial days of hot weather.(8)
Under these conditions, the modest amounts of salt in commercial sport drinks can off-set salt loss in sweat and minimize medical events associated with electrolyte imbalances (e.g., muscle cramps and hyponatremia).
If carbohydrate concentrations are too high, delays in gastric emptying can be observed when mixing a sport drink from a powder; be sure to follow the directions and add sufficient water to avoid overly concentrated solutions.(9)
Best: IV rehydration with normal saline has produced mixed reviews in terms of athletic performance.(12,13) Although most studies have shown IV and oral rehydration to be the equivalent in rehydration techniques, the comparison hasn't been applied to first responders working in PPE or thermal protective clothing. Introducing fluids directly into the plasma volume may be beneficial when the environment and protective equipment impair thermoregulation. Two clearly superior aspects of IV fluid administration are the ability to deliver larger volumes of fluid in a short period and the effect of mild cooling.
It's not unusual for a firefighter to lose 1Ï2 kg of fluid in a prolonged incident or an exceedingly hot environment. Ideally, fluid replacement should equal fluid losses, requiring the firefighter to consume as much as 2 L of fluid before returning to the incident. More than a liter of fluid in the stomach will likely cause gastric distress. This can be overcome by providing a rapid bolus of normal saline through a peripheral arm vein. Additionally, a rapid bolus of normal saline will result in core cooling of as much as 1.0_ F.(14)
How do I cool personnel in the rehab sector?
Good: Firefighters and other emergency responders must remove their turnout gear or jackets and be sheltered from the environment. Optimally, both the turnout coat and pants of firefighters should be removed to aid in passive cooling. If this isn't possible, the turnout pants should be pushed down below the knees while the firefighter is seated in the rehab sector. In many cases, the firefighter will continue to warm as metabolic heat is produced even if the turnout gear is reduced. If passive cooling is employed, expand the rehab time before returning to the incident to allow for core cooling.
Better: Passive cooling is inefficient, especially in hypohydrated individuals. Place hyperthermic emergency personnel into air-conditioned vehicles to aid in cooling. Misting fans have also become popular devices in rehab units. Although moving air around a person in need of rehab will enhance convective heat loss, the application of water mist will be effective only if the relative humidity is low. Even under optimal conditions, the misting fan will reduce core body temperature less than 1.8_ F (1.0_ C) during a 30-minute exposure.(15)
Best: Applying cooling modalities directly to the responder are the best regimens for cooling. Some level of evidence supports the effectiveness of powered cooling vests and forearm immersion, which take advantage of the great conductive capacity of water. These methods can be effective modalities for cooling mildly hyperthermic emergency personnel but require a significant investment to place these items on a rehab unit.
Forearm immersion takes advantage of the many superficial arm veins by placing the forearms and hands into cold water, enhancing the convective transfer of heat from the blood to the water. Studies have shown this technique can result in 0.5Ï1.5_ C cooling in a 30-minute exposure.
Powered cooling vests use a cooling source similar to a portable air-conditioner to chill a fluid that's then circulated through a vest worn by the firefighter while in the rehab sector. A variant on the theme are vests containing a material that feels cool after being immersed in water. These vests feel cool when first applied but can quickly become insulators once the initial cooling has been consumed.
Cooling for Exertional Heatstroke
Exertional heat stroke (EHS) is the life-threatening endpoint of untreated hyperthermia resulting from exercise or work in hot environments. Victims of EHS are typically unconscious or have significantly altered levels of consciousness, but may have brief lucid intervals.
Although sick and unable to thermoregulate in classic heatstroke cases, EHS victims will be extremely diaphoretic, having worked under conditions that make them appear ˙wet.Ó This is a key feature to note in the rehab sector. Don't confuse regular heat exhaustion with the more severe EHS because they're not ˙dry.Ó Observe all the monitoring parameters available, the temperature and the clinical picture in order to determine how severely affected the firefighter may be from the heat.
In some sporting events, the rate of EHS is as high as 1 to 1,000. Once EHS has occurred, the severity is directly related to the time the core body temperature remains above the critical threshold. There's a misconception in the medical community that treating EHS by immersion will result in further heating and heat stress from peripheral vessel constriction. However, cold water immersion (CWI) is the gold standard for treating EHS.(16) The conductive capacity of cold water placed directly against the skin far exceeds any impairment of skin blood flow from vasoconstriction.
CWI isn't without risk. If the EHS victim is overcooled, there's a risk of shivering or hypothermic afterdrop. Hypothermic afterdrop occurs if the body is overcooled and requires re-warming. This can be avoided with proper precautions. Any prehospital provider tasked with treating EHS should have the required equipment to measure rectal temperature. A flexible thermistor should be placed 10 cm into the rectum and remain in place during CWI.(17) This will allow the patient to be removed from the immersion when the core temperature reaches 102_ F (39_ C). In cases where a rigid rectal thermometer is used, the cooling rate of 0.2_ can be used to calculate when 39_ will be reached. This allows the victim to be removed before too much cooling is applied. Once initial cooling has been accomplished, the EHS victim can be transported to the emergency department.
In many instances, the resources for CWI won't be readily available. The need for immediate cooling is still imperative. An effective mode of cooling used by field military units involves wrapping the victim in sheets soaked in ice-cold water, readily accomplished by placing two sheets into a cooler of ice water. Remove the clothing from the victim, and wrap one sheet on the anterior and lateral skin surface of the supine patient. After applying for 60Ï90 seconds, return the sheets to the cooler and apply the second sheet. Monitor the core temperature during this procedure and discontinue when a core temperature of 102_ F (39_ C) is achieved.
Providing Nutrition during Rehab
During a prolonged incident, it'll be necessary to provide some form of nutrition to working firefighters. In many cases, this nutritional support can be satisfied with small foods easily eaten cold and without utensils. It's important to ensure nutritional support is balanced. Most sport nutritionists recommend snacks that are primarily complex carbohydrates to maintain blood glucose levels with some protein and a lesser amount of fat. Many of the individually wrapped sport snacks meet these requirements and have the advantage of a long shelf life. Be sure to check the labels and have crews try items before purchasing any for your rehab operation. Supplements won't be useful if the taste prevents them from being eaten on the scene.
For truly prolonged incidents, it will be necessary to provide major nutritional support, usually in the form of a hot meal. In many cases, you will need to rely on outside agencies operating a mobile canteen to meet these needs. Preplan with these agencies to confirm the items being provided can be brought in sufficient quantity and meet the nutritional needs of the crews.
Fireground rehab is an essential component of any incident that may save lives and improve the health of responders. Preplanning for rehab is essential to ensure you have the means and protocols to monitor firefighters and to provide effective rehydration and cooling. It may also be necessary to provide nutritional support during extended incidents. Caring for the health and safety of firefighters during an incident will not only ensure their ability to work at the current incident but allows the crew to return to service, ready to answer the next alarm.
1. Karter M Jr, Molis J. ˙Firefighter injuries for 2004.Ó. NFPA Journal 2005;99:50-57.
2.Dickinson E, Wieder M.Emergency Incident Rehabilitation,UpperSaddleRiver: Pearson Prentice Hall; 2004.
3. Bouchama A, Bridey F, Hammami M. ˙Activation of coagulation and fibrinolysis in heatstroke.Ó. Journal of Thrombosis and Haemostasis 1996;76:909-1015.